Copy film for lenticular sound tracks



July 31 1945 c. J. DIPPEL ET Al. 2,380,585

COPYFILMS FOR LENTICULAR SOUND TRACKS Filed April lO, 1941 3 Sheets-Sheet 1 3V Sheets-Sheet 2 July 31 1945' c. J. DIPPEI. ET AL.

COPYFILMS FOR LENTICULAR SOUND TRACKS Filed April 1o, 1941 .July 31, 1945.

COPYFILMS F Filed April 10, 1941 J.r DIPPEL ET AL OR LENTICULAR SOUND TRACKS 3 Sheets-Sheet 5 I mi.

Ih max.

y aienied L.iuly 31, i945 COPY FILM Foa LENTICULAn sonno y TRACKS n I Cornelis Johannes Dippel and Klaasfannes vKeuning. Eindhoven, Netherlands. and Honore Mortsel, anden Joseph Jules Verkinderen,

Laurent Henri Van `l-loesienberghe1 Berchem. Belgium; vested in the Alien Property Custodian Application April 10, `1941, Serial No. 387,1974 Inthe Netherlands June/2l, 1938 6 Claims.

yOurA invention relates to films1 for copying lenticular sound tracks.

Our invention is particularly concerned with films ior copying sound records having an optically reproducible sound track withdepth variations and in most cases width variations as described in ourcopending application Serial No. 280,188, filed June 2G. 1939, and of which the present application is a rcontinuation-impart.

.Such a sound track has a. wavy surface which is not parallel to the surface of the carrier, and when it is copied', for instance by transmitted light, the light rays will be partly retracted at the surface of the track. Consequently the luminous intensityoi the light striking the copy which, upon printing, fall below the threshold value ofthe blackenins curve oithepcsitive. It should also be noted that, with the copying mcthodspositive material and developing methods lm is determined not only' by the bright and black portions of the sound track, but also by the amount of the refraction. This refractive phenomenon will hereinafter be referred to. as a "lens effect and a sound track which has this property will be referred to as a lenticular track. f

We have found that when such sound tracks are photographically copied twice. there is the difilculty that dark striae are produced in the non-blackened portions of the copies and 'cause distortion of the sound during reproduction. This diiiculty is particularly prevalent in copying -a sound record comprising a transparent 4sound track having both width and depth variations and opaque" surroundings, such as are produced with a cutting tool having a V-shaped cutting edge in the manner described in the U. S. Patent #1,919,116 to James A. Miller. The term "opaqueg portion as used herein and in the claims is to be understood to mean a portion whose transparency to the type or light used for copying or scanning is very small in comparison with that oi* the transparent parts.

For a complete understanding of the problems in copying such sound'records it should be'noted that it apositive copy, to be referred to as a posii tive, made from such a sound record is to be suitable for reproduction with photo-electric cells it must satisfy two main requirements. First, the blackening difference between the "opaque" and the transparent portions Lof the positive must have a minimum value of 1.2 in order to produce a suilicient diiierence in luminous intensity onv the cathode of the photo-electric cell. Secondly, no

dark striae or blurred transitions should be present on the transparent portions of the positive."

To obtain such a positive, the negative used in the copying should either have no variations in the Mineduc portion or should have variations used at the present time, it is necessary to have a minimum blackening vciiierence of about 1.0 between the sound track and its surrounding on the negative in order to obtain the desired blackening difference of 1.2 between the bright and dark parts of the sound track on the positive. lWith present-day copyingy methods, a maximum gamma'of 2.4 is seldom exceeded in copying in view of the picture films to be developed by means of the same copying device. and with such a gamma value it is just possible to obtain the above-mentioned blackenina difference 'of i2 on the positive. with the minimum blackening differences of about 1.0 on the negative.

By using a positive iilrn, for instance with e smaller foot of the blackenins curve than is used at present or by being allowed to raise the admis ,sible gamma. the required blackening difference on the positive can ybe obtained with a biackenins difference of less than 1.0 on the negative. but in this case it would probably not be possible to so lower than lib.

If the condition imposed on the minimum blackening diierence oi the negative is not sottise ed and from this negative is printed a positive having a blackening difference oi 1.2 between track and its surroundings. opaque striations will arise in the bright Vsoundtrack oi the positive which. as stated, have a vdeleterious effect on the reproduction.

Ii it is desired to obtain apositive without striae in thel track. onevmight maize the negative 'so that thezminimium blackening caused by the lens eiect or the original track amounts to more than l. ior instance to 1.4i.` However, this has the drawback that the stronger blackeninfg so octurrirngA due to the lens eilect, is accompanied by an effective reduction oi' the amplitudes, more particularly of the high frequencies due to diu= sion.

Above we have stated the factors which have to be considered when a positive copy is made from an initially-positive soundtrack; However. analogous factors apply incopyins a negative sound track involving lens effect in its transitan According; to the invention the copy c light sensitive emulsion layer having a blacken'ing l of the copying light and are curve the derivative o!y which' has either aminl. 'i

- mum or exhibits a decrease with increasing ex-g' ,posure at a blackening o! 0.5-1.8 `and a derivative below 0.6 in the region o!y the usualblackens. i If the derivative of the blackenin'g curve .either has a minimum orexhibits a decrease with in# creasing exposure this signifies in both cases vthat the derivativein this region of 0.51.8 has a value which is vsmaller than that in the immediate adjoining region having a smaller exposure.

In other words the derivate is locally-'smaller than in the immediately adjoiningpart ofthe .blackening curve towards the side of smaller exy posure. Consequently the blackening variations;

produced on such a illm by the lens effect will be smaller than when using a copying iilm having a ,tion.. v A.

The tllm carrier shown in Fig. l comprises a supporting layer I of transparent material', such escasas' -1 rigs. 's to irinuusive are magnum-mammation curves for use in describing the methodof the '-'inventiom and f l Figs..12 and 13 are sectional views on enlarged scales otsensitized` illms according to the inven as Celluloid, a cuttinglayer'! oi transparent material, auch as gelatin, and a Vthin 'covering layer Q of opaque material, such/asa colloldallynormal blackening curve and as a result the i,

. maximum blackening may also become smaller( Since the blackening variations on thisl copy are smaller, the variations in luminous intensity of any'print made from this copy are also smaller so that` the blackening vvariations on the print may remain below the threshold value of` the blackening curve even with a sufllcient intensity l no longer perceptible in the sound track eventually obtained. Y The term minimum" 'as used herein and in the claims is to be understood to include the case in which the derivative falls to a definite minimum value and remains at this value over a i portion of the blackening curve. i

With the above-mentioned minimum difference of 0.8 between the minimum blackening due to lens effect and the transparent parts ofthe sound negative sound track. on a. positive illm and obtain the required blackening difference .between the sound track and its surroundings.

In copying mechanically-recorded sound tracks inaccordance with the lnventionone may depart from the technique used in printing normal sound f' dispersed'metal. `A cutting tool 80 having a V- shaped cutting edge with a large apical angle is .vibrated in accordance-with the sound vibrations to `be recorded inthe direction of the doubleheaded arrow A while the nlm is moved at a constant speed in the direction of arrow B to thereby produce a sound track l having both width andv sdepth variations. Such methods of recording have been described in detail in the above-mentionen` Patent #1,919,116, and the track l is suitable for optical reproduction withv the aid Vof a photo-electric cell. However, i! the track is to be i photographicallyfprintei dimculties arise dus to the lens effect, as will be set forth in more detail with reference to Figure 2. 1

As shown inl Figure 2, the carrier of. Fig. .l is

placed on top of a copying nlm comprising a.

- transparent Celluloid layer l provided with a z track onthe negative, it is possible to print'this layer] of a sensitized N emulsion. Inprinting Y trackl,l which has an Vunclulated surface, the rays Voi' the copying light, indicated by reference numeral'liL lare retracted at the undulated surface of the track with-the result that the layer `l is unevenly illuminated i. e. vspots l. have a great luminous-intensity and spots 8 have a small lumi nous intensity. Only a very small 'quantity o! -light iinpinges, on the portion 9 of the emulsion 5 which is beneath the spots where the cutting tool 'has not penetrated into the opaque" coatrn the further discussion-the quantity flight l' impinging upon spots 'I ofmsximum illumination films, vizi. that the record has always to take place in the straight part of the blackening'4 curve and consequently in copying one may use films whose blackening curve isl diil'erent from the normal one.

The expression "region of usual blackening is to be'understood'to mean a region which. extends between the minimum blackeningwhich gives a good copy and the blackcning at which theine tensity due to the diffused ugnt beyond the track becomes so high that the spaces between the peaks of the amplitudes of the ytrack are also blackened to an undesirable degree. Withpresent-day photographic films the minimum limit is about a blackening oi' about laand the maxi- `mum limit is a blackening of 'about 1.8.

In order that the invention can be clearly understood and readily carried into effect we shallv described the same in morefdetail with reference to the accompanying drawings in which'.

Figure l is a.- perspective view on'an enlarged scale of a portion of a lm carrier provided with a mechanically-recorded -and optically-reproduciblesoun'd track and shows the cutting tool ior producing the track.. u f

Fig. 2 is a-sectional viewon an enlarged scale oi' the carrier of Figure l placed on top of a sensitized copying film,

Figs. 3 and 4 are blackening-illumination curves of the positive and negative illms respectively upou which the sound track of Figure l is copied. f

intensity will be denoted by. Ih au., the quantity voflighi: izhpinging on spots! yof minimum illumination intensity will be indicated by Ih :niemand the light passingthrough the fopaque coating 4 will be denoted by I.. `i-urthe'rmore, the values Iz. Isminpand In mx. will also be designated 'by the. reference numbers Ill, il land i2.erespectively. The blackeningsbrought about on the first copyv v bythese illumination intensitiesv willbe denoted by Dz. Dh mln. and Dh n'mx; respectively.

Fromthe above'it appears that in printing `the initialv or original mechanically recordedsound film" on anegative fllm.,a sound track having' blackenings between Dh mm. landDh mlx.- is obtained. .'Due to this. principally three illumina tion intensities will have to be considered in printf ing this negative film on a positive lm. One

,would be inclined to cause the-variations in illumination intensity brought about by the blackening variations producedby the lens' effect in the original sound track. to fall below the threshold valueof the blackening curve of the positive. Howeveiuvfrom the following discussion it will bc seen that there are drawbacks to such a' pro. cedure. f

As has been mentioned above. ka positiw` dc.- signcd for photo electrical reproduction must sui isfy two main conditions.` One oi tlicsc is that thc minimum blackening nf 1.2 determines. ai n. given value for the gamma, tht` required minmum blackening difference between the bright parts and those parts which are blackened lcast due to thelens eiiect onthe negative (D, and cause of lens effect, a maximum illumination Dh mm). f

Fig. 3 illustrates the blackening and ratios of illumination intensity for a normal positive nlm developedy in Kodak developer Die. A minimum blackening difference (I3-2|) of 1.2 is desirable. I f this nlm is developed under the most favorable conditions to a gamma .of 2.4, this would requirean illumination indicated by reference numeral i4. namely that there be no black striae in the trans'- parent parts of the copies, itis necessary that the illumination l5, which results from the light value 81 of the blackening curveof the positive.

To satisfy the second condition,v

intensity l2 up to twenty times as strong as illumination H already occurs. The blackening to,

As appears from the iigure the range of illumina'- tion lies partly in the foot of the blackening curve, and, thus the difference between the logarithme .of the illumination intensities indicated by refers and I must have a minimum black films, particularly in view of the condil tions tobe met by the picture image, to a gamma lying between 1.8 vand 2.4 so that on producing sound lms lfor commercial use, these limits of the' gamma must be taken into account. If'the development of the positive film goes only to a gamma of 1.8, then an illumination as indicated by lin Figure 3 is necessary to obtain the required blackening difference IS-ZI, From Figures 3 and 4 it appears that in such a case the difference between the logarithme of the corresponding illumination intensities l5 and I6 has a minimum value of 1.1. vWith these differences in illumination intensity, the illuminations l5 and ll caused by the lens effect may be held below the threshold value 81 of the blackening curve of the positive nlm while at the same time conserving on the positive theminimum blackening, difference of 1.2 required for satisfactory reproduction by a photo-electric cell.

The stated illumination value determines the conditions which must be satised by the blackenlng difference on the negative, from which the above-mentioned positive is tobe printed. Thus, as shown in Fig. 4 the minimum blackening difference -19 i. e. Dh nim-Dz in the sound track on the negative must be at least 1.0 and which corresponds to this maximum illumina- ;tion, may new have such a value that, due to printed from this negative. lo

Upon printing the original sound record on a copying llmaccording to the invention having a blackening curve such as shown in Fig. 5,.the

``abovementioned clilculties can be -obviated .In

fact, the curve represented in Fig. 5 has a smaller gamma in the range of the usual blackening than inithe immediately adjoining region of weaker blackening.' The dot-anddash line 6l represents the course of the gamma through the blackening region. In printing, the variations in luminous intensity between Il and l2 (In mm. and In max.) lie in that range so that the Ilolaclsening 30 becomes materially smaller than in printing the nlm exhibiting the same intensity difference on a nlm having anormal blackening curve. However, as the maximum blackening 30 is smaller, the resolving power is higher with the'result that a greater marginal denition is obtained. At the same time the blackening dinerence -36-29 (Dn :uu-Dn min.) is smaller than that of magnitude. This makes it possible to produce a good second copy (positive) 'on a filmhaving a normal curve, as is shown in Fig. 6.

As shown in Fig. 6, the variations SZ- due i to Dn mm. and of the negative mayY easily fall l1below the threshold value 8l of the blackenlng curve, while in spite of this the intensity 40 di'erence al--SZ is sumcient to produce on this second copy a blackening 35 exceeding 1.2 relatively to the fog t4 in the track i, 2..

If, for some reason, for instance because the gamma of the second copy cannot 'be sumciently raised, the illumination must be raised to such a degree for obtaining a sumcient blackening 35 that the Variations 32-33 `fall partly above the 7 threshold vaiue a1, as shown 1n Fig. '1. then the preferably greater than 1.1 in order to ensure in all cases good results on the positive. Considering these` conditions, and a gamma of the negative determined by the conditions to be mentioned hereinafter, it is not diiiloult to determine the illumination ll required therefor. The illumination of the negative, which is to be understood to be the difference between log In mm. and

log L, depends on the blackening of the opaque layer" 4 of the original sound record, which for tained. It appears that inthe most unfavorw able case the negative must, for this purpose, be developed to a gamma of 1.0.

However, it should -be remembered thatbeblackenings 391-40 are weaker in the iinal sound track.

Films having a blackening curve such as shown in Fig. 8, in which' the gamma as indicated by the dot-dash line t2 exhibits a decrease with increasing illumination intensity and acquires a negative value, yield the same advantages. As'shown in this ngure, an illumination I0 yields a blaclreningr 36, whereas in`the region of the variations in luminous intensity lli-l2, there are blackenings between 3l vand 38 onV the negative. As the maximum blackem'ng 3@ is materially smaller than the maximum blackening on a normal nlm, 'we obtain the same advantages set forth above.

The blackening curve shown in Fig. 9 comprisesat least two parts having different gammas, as appears from the dot-dash curve 63. In

. the region below the usual blackening, the gamma has a minimum value of about l, and in the region of the usual blackening the value of the gamma falls below about 0.6 so that in thisrange the blackening remains small due to Ih max. As

va result, the blackening variation t6-t5 is small so that the above-mentioned advantages can also be obtained therewith.

Figs. l0 and l1 represent a blackening curve whose derivate represented by the dot-dash curves 64 and 65 respectively approach zero in the usual blackening region over a .large illumination interval. If the region of intensity variations caused by the lens effect is located in this illumination interval, the first copy obtained will have a perfectly uniform blaokening 53 in the sound track so that even in the rst copy of the blackening variations due to the lens effect are entirely eliminated. By suitably positioning that part of the curve in the region of usual'blackening which approaches to zero, the blackening difference 52-53 is, moreover, larger thanA 1.0. Y

The curves referred to above can practically be obtained in two different ways, viz. by

I. Controlled development of normal 'photographic emulsions-By abruptly interrupting the development, the emulsion layer is developed only to a definite depth so that even if the light eifect has penetrated to a greater depth, the emulsion layer will be'blackened only to a deiinite depth. As a result there will be obtained a blackening curve such as shown in Fig. l1 which has. a decidedly horizontal part above a definite blackening value. Such a'iilm is shown in'Fig. V12, in which the reference numeral 5B denotes a Celluloid supporting layer and a reference numeral 59 indicates an 'emulsion layer in which the sound image 60 is produced only to a certain depth. lThis controlled development may be obtained by adding to the developing bath a high percentage, about 10%, of alcohol, glycerin or acetone, or about 20% of sodium sulphate. u

II. By normal development of a film with two sensitized emulsions of a decidedly dierent character or by ldefinite kinds of light- These diierent emulsions may be provided in two distinct layers. If the top layer is much more sensitive than the second layer, for instance the top layer is a panchromatic and the second layer is a non-panchromatic layer, or if the top layer is a silver bromide layer and the second layer is a paper-silver-chloride layer respectively, a blackening curve such as shown in Fig. 10 is eventually obtained, i. e. a curve comprising two separate parts connected by a substantially horiness between both emulsions.

In all cases referred to above an anti-halation layer may be provided for reducing diffusion.

As an alternative, a very thin emulsion layer of the order of magnitude of 5 microns or less maybe provided on an anti-halation substratum. If the thickness and sensitiveness of the emulsion layer are judiciously chosen, the maximum blackening oi this layer just lies .in the range of usual blackening, namely between about l and 1.8. Thus, a bla'ckening curve such as shown in Fig. 8 or Fig. 1l is obtained. Similar results may .be secured by the use of a Very thin emulsion layer on a substratum of a light sensitive emulsion layer containing a dye, in combination with a special printing light being readily absorbed in said dye. As such we can use a sub- In all cases, howrassesses' vwhich is very favorable for this purpose and stratum containing tartresine in combination with blue printing light. A lm of this type is shown in Fig. 13 in which a Celluloid layer Eiffi carries' an anti-halation layer 555 and a thin emulsion layer 5b in which a sound image Eil is produced.' Y

Although we have described our invention with reference to specific `examples and applications, We do not wish to be limited thereto because obvious modications will readily present themselves to one skilled in this art.

What we claim is:

1. In the copying of a sound carrier having a lenticular sound track characterized by depth and width variations which refract iight passed through the sound track and produce a copying light-beam ofA non-uniform intensity, the method of photographically,producing a copy of said sound traclr precluding the formation of striae due to the non-uniform intensity oi the copying light-beam, comprising. the steps oi passing light through. the sound tracir, and ei;- posing with the resulting light-beam of non-- uniform intensity and developing, a copy lin comprising a light-sensitive silver-halide emulsion layer so that said light-sensitive layer has a blackening curve characterized by a variable derivative at a blackening of 0.5 to 1.8 and a derivative of zero in the region of blaclrening of l to 1.8,.the said exposure having a value at which the range of the light intensity variations produced by the refraction oi light through the carrier falls within the region of zero derivative of the blackening curve and the formav tion of striae due to the non-uniform intensity of the copying light-beam is substantially precluded. j

2. In the copying of a sound carrier having e. lenticular sound track characterized by depth and Width variations which refract light passed through the sound track and produce a copying light-beam of non-uniform intensity, the method of photographically producing a copy or" said sound track precluding the formation. oi striae due to the non-uniform intensity of copying light-beam, comprising the steps oi passing light through the sound track, and exposing with the resulting light-beam of non-uniform .intensity and developing, a copy film comprising a lightsensitive silver-halide layer having a thickness not exceeding 6 microns, so that said light-sensitive layer has a blaclrening curve characterized by a variable derivative at a bias-herring or 0.5 to 1.8 and a derivative of zero in the region of blaclrening of l to 1.8, the said exposure having a value at which the range of the light intensity variations produced by the refraction of light through the carrier falls within the region of zero derivative of the blaclrening curve and the formation of striae due tc the non-uniiorrn intensity of the copying light-beam is substantially i precluded. i

light through the sound-track, and exposing with the resulting light-beam of non-uniform inten-- sity and developing, a copy nlm comprising a light-sensitive coating including a layer ci a light-sensitive silver-'halide emulsion and a covering layer of a light-sensitive 'silver-halide emulsion of diierent characteristics than the .sensitive silver-halide emulsion layer, so that first emulsion, so that the coating has a blackl ening curve characterized by a variable derivative at a blackening of 0.5 to 1.8 and a derivative of zero in the region of blackening of 1 to v 1.8, the said exposure having a. value at which the range of the light intensity variations produced by the refraction of light through the carrler falls within the region of zero derivative of the blackening curve and the formation of striae due to the non-uniform intensity of the copying light-beam is precluded.

4. In the copying of a sound carrier having a lenticular sound track characterized by depth and width variations which refract light passed through the sound track and produce a copying light-beam of non-uniform intensity, the methodiof photographically producing a copy of said sound track precluding the formation of striae 'due to the non-uniform intensity of the copying light-beam, comprising the steps of passing light through the sound track, and exposing with the resultingl light-beam of non-uniform intensityr and developing, a copy film comprising an antihalatdon substratum and a light-sensitive coating including a layer of a light-sensitive silverhalide'emulsion and a covering layer of a lightsensitive silver-halide emulsion of different characteristics than the ilrst emulsion, so that the said light-sensitive emulsion layer has a blackening curve characterized by a portion of said curve having a gamma of minimum 1 below a blackening of 1 and a second portion having a gamma below 0.6 with a minimum of zero in the region of blackening of 1 to 1.8, the said exposure having a value at which the range of the light intensity variations produced by the refraction of light through the carrier falls within said second portion of the blackening curve and the formation of striae due to the non-uniform intensity of the copying light-beam is preeluded. Y

6. In. the photographic Vreproduction of a sound carrier having a lenticular sound track with depth and width variations whereby light passed through the sound track is retracted and rendered non-uniform in intensity, the method of producing a positive free from striae formation due to the non-uniform intensity of the copying light beam, comprising the steps of passing light through the sound track, exposing with the resulting light-beam of non-uniform inten-ls sity and developing, a negative copy silver-halide lm so that said negative has a blackening curve characterized by a variable derivative at a blacky ening of from about 0.5 to about 1.8 and a decoating has a blackening curve characterized' to 1.8 and a derivative of zero in the region of blackening of 1 to 1.8, the said exposure having a value at which the range of the light intensity variations produced by the .refraction of light through the .carrier falls within the region of zero derivative of the blackening curve and the formation of striae due to the non-uniform intensity of the copying light-beam is precluded.

5. In the copying of a sound carrier having a lenticular sound trackl characterized by depth and width variations which refract light passed through the vsound track and produce a copying light-beam of non-uniform intensity, the metho'd of photographically producing a copy of said sound track precluding the formation of striae due to the non-uniform intensity of the copying light-beam, comprising the steps of passing light beam is substantially precluded, passing light through the negative so exposed and developed.

exposing with'the resulting lightgheam and de" of said light to a value at which the portion of the light beam passing through the negative copy of the sound track has a maximum intensity below the threshold value of the blackening curve of the positive to thereby produce a posi-i tive copy oi the sound track free from striae.

formation.

CORNELIS JOHANNES DIPPEL.` KLAAS JANNES KEUNING.

HONOR JOSEPH JULES RENE LAURENT HENRI VAN o HOESTENBERGHE. 

